M3.68: groups, layers and type have their own fills, strokes and effects, with Contents and Characters rows

A group's or layer's own fills and strokes paint every member's geometry, below or above the
members as the new contents slot (Appearance.contents_index) says; its geometry effects reshape
the members as one piece and its raster effects apply to the composite (one combined shadow),
respecting knockout groups. Type's own fills and strokes paint under or over its characters.
Render, SVG/PDF (via bake) and Expand Appearance evaluate them alike.

Commands: appearance.* / effect.* take target: "object"|"contents" and layer ids;
appearance.moveItem moves the Contents slot (from: "contents") or an item across it
(contents); appearance.targetContents selects a group's members. Graphic styles applied to a
group now style the group itself. The Appearance panel shows Contents/Characters rows that
drag, and double-click to target the members or edit the characters' paint.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/render/src/fx.rs

@@ -15,7 +15,10 @@
 //!
 //! The same applies to one fill or stroke's own raster effects (around that item alone) and to
 //! type, images, symbol instances and live objects ([`Renderer::draw_object_fx`]): their art is
-//! drawn offscreen in the filter layers, reshaped first by their geometry effects.
+//! drawn offscreen in the filter layers, reshaped first by their geometry effects. Groups and
+//! layers with an appearance of their own take the same path with their evaluated art
+//! ([`effects::evaluate_container`]: their fills and strokes painting the members, their geometry
+//! effects reshaping them), so their raster effects apply to the composite (one combined shadow).
 
 use std::sync::Arc;
 
@@ -45,9 +48,15 @@ pub(crate) fn has_fx(n: &Node) -> bool {
 }
 
 /// Does `n` carry visible object-level effects that only apply through its art (type, images,
-/// symbol instances, live objects; see [`Renderer::draw_object_fx`])?
+/// symbol instances, live objects), or is it a group or layer with an appearance of its own (see
+/// [`Renderer::draw_object_fx`])?
 pub(crate) fn has_object_fx(n: &Node) -> bool {
-    effects::needs_outline(n) && visible(&n.appearance.effects)
+    (effects::needs_outline(n) && visible(&n.appearance.effects)) || effects::has_container_appearance(n)
+}
+
+/// Is `n` a group or layer (whose evaluated art keeps its knockout setting)?
+fn is_container(n: &Node) -> bool {
+    matches!(n.kind, NodeKind::Group { .. } | NodeKind::Layer { .. })
 }
 
 /// What [`Renderer::raster_fx`] paints effects around.
@@ -127,6 +136,18 @@ pub(crate) fn visual_bounds(n: &Node) -> Option<Rect> {
 /// the subtree (a shadow can reach the view while its object is outside it).
 pub(crate) fn cull_bounds(n: &Node) -> Option<Rect> {
     match &n.kind {
+        // The evaluated art (its fills, strokes and geometry effects) and the raster effects' reach.
+        _ if effects::has_container_appearance(n) => {
+            let art = effects::evaluate_container(n);
+            let art = art.as_ref().unwrap_or(n);
+            let b = if art.clips() {
+                art.visual_bounds()
+            } else {
+                art.children()?.iter().fold(None, |acc, c| vectorcraft_geom::union_opt(acc, cull_bounds(c)))
+            }?;
+            let o = effects::outset(&n.appearance.effects);
+            Some(b.inflate(o, o))
+        }
         NodeKind::Layer { children, clip: false, .. } | NodeKind::Group { children, clip: false } => {
             children.iter().fold(None, |acc, c| vectorcraft_geom::union_opt(acc, cull_bounds(c)))
         }
@@ -375,7 +396,8 @@ impl Renderer {
 
     /// The art [`Self::draw_object_fx`] draws for `a` (cached by `Arc` identity when `cache`):
     /// reshaped by its geometry effects, else type and images as themselves and the others as
-    /// their evaluated art; without the object's transparency and effects.
+    /// their evaluated art (groups and layers: [`effects::evaluate_container`], keeping their
+    /// knockout setting); without the object's transparency and effects.
     fn fx_art(&mut self, doc: &vectorcraft_doc::Document, a: &Arc<Node>, cache: bool) -> Arc<Node> {
         let key = Arc::as_ptr(a) as usize;
         if cache
@@ -390,8 +412,10 @@ impl Renderer {
             }
             _ => None,
         };
+        let container = is_container(a);
         let art = match effects::reshape(a, symbol.as_ref()) {
             Some(r) => r,
+            None if container => effects::evaluate_container(a).unwrap_or_else(|| (**a).clone()),
             None if matches!(a.kind, NodeKind::Text(_) | NodeKind::Image(_)) => (**a).clone(),
             None => effects::outline_art(a, symbol.as_ref()).unwrap_or_else(|| Node::group(a.id, vec![])),
         };
@@ -399,8 +423,9 @@ impl Renderer {
             opacity: 1.0,
             blend: Default::default(),
             isolate: false,
-            // One element: its pieces never knock each other out.
-            knockout: vectorcraft_doc::Knockout::Off,
+            // One element: its pieces never knock each other out (a group's members still do as
+            // its knockout setting says).
+            knockout: if container { a.knockout } else { vectorcraft_doc::Knockout::Off },
             mask: None,
             appearance: vectorcraft_doc::Appearance { effects: vec![], ..art.appearance },
             ..art